Conventionally, integrated millimeter-wave receivers, such as those used in automotive radar at 77 GHz, are tested either after production using expensive probe stations and measurement equipment or only indirectly via other measurements at low frequencies. The former is costly and time inefficient, while the latter provides only a general indication of circuit performance rather than an oft-desired thorough characterization.
While the integration of test signal sources on chip has been proposed, such a solution can be imperfect because the properties of the test signal vary with process variations and are not known exactly. Therefore, it can be difficult to obtain precise measurements, and a need for accurate and cost-effective testing remains.